Scrapy: Arbitrary Module Import via Referrer-Policy Header in RefererMiddleware
Scrapy is a high-level web crawling and scraping framework for Python. From 1.4.0 until 2.14.2, RefererMiddleware in scrapy/spidermiddlewares/referer.py treated a Referrer-Policy response-header value that resembled a Python import path as a referrer policy class, imported the referenced object, and called it. A malicious website could supply a callable such as sys.exit and terminate a crawler processing the response. This issue is fixed in version 2.14.2.
Scrapy versions up to 2.13.2 are vulnerable to a denial of service (DoS) attack due to a flaw in its brotli decompression implementation. The protection mechanism against decompression bombs fails to mitigate the brotli variant, allowing remote servers to crash clients with less than 80GB of available memory. This occurs because brotli can achieve extremely high compression ratios for zero-filled data, leading to excessive memory consumption during decompression.
Authorization Header Leakage in scrapy/scrapy on Scheme Change Redirects
In scrapy/scrapy, an issue was identified where the Authorization header is not removed during redirects that only change the scheme (e.g., HTTPS to HTTP) but remain within the same domain. This behavior contravenes the Fetch standard, which mandates the removal of Authorization headers in cross-origin requests when the scheme, host, or port changes. Consequently, when a redirect downgrades from HTTPS to HTTP, the Authorization header may be inadvertently exposed in plaintext, leading to potential sensitive information disclosure to unauthorized actors. The flaw is located in the _build_redirect_request function of the redirect middleware.
Scrapy 1.4 allows remote attackers to cause a denial of service (memory consumption) via large files because arbitrarily many files are read into memory, which is especially problematic if the files are then individually written in a separate thread to a slow storage resource, as demonstrated by interaction between dataReceived (in core/downloader/handlers/http11.py) and S3FilesStore.